In continued cooperation with Prof. J. M. Cook and his coworkers at the University of Wisconsin-Milwaukee, the synthesis of di- and polycyclic ring systems composed of fused cyclopentane rings ("polyquinanes") has been developed further. The approach chosen is based on the ready stereospecific formation of derivatives of cis-bicyclo[3.3.0]octane-3.7-dione (1) from 1.2-dicarbonyl compounds and esters of 3-oxoglutaric acid (the "Weiss reaction"). This year's effort was directed mainly towards the introduction of the maximum number of double bonds into the polyquinanes so obtained; the resulting products would be of great theoretical interest. However, the experimental difficulties are great, and the goal has not yet been reached. The possibility of introducing substituents into positions 2+4 of the bicyclo[3.3.0]octanedione system, suggested but not proven in the literature, has been established. In cooperation with Profs. Merlini and Nasini, the structure of the mold pigment elsinochrome A, derived by us earlier, has been confirmed unequivocally by x-ray crystallography.